• Preheat oven to 400°F (204°C). Spray a large 9 x 13-inch baking dish with nonstick spray (or lightly oil).

Cook Pasta:

• Bring a large pot of salted water to a boil. Add penne, then cook until al dente. (Do not overcook.)
• Drain pasta, then set aside.

Make Sauce:

• While pasta is cooking, heat olive oil over medium-high heat in a large skillet.
• Add onions and bell pepper to oil. Cook, stirring frequently, until they begin to brown.
• Stir mushrooms into pan and saute until they begin to brown, stirring often.
• Add squash / zucchini to pan, then cook until lightly browned, stirring frequently.
• Season veggies with salt, then reduce heat to medium.
• Mix pasta sauce into vegetables and cook until hot, stirring frequently.
• Add spinach to sauce. Cook until wilted, stirring constantly.
• Stir basil into sauce. Remove sauce from heat, then season to taste with additional salt, if needed.

Assemble + Bake:

• Stir pasta into sauce, then mix in 1 ½ cups of the cheese.
• Transfer pasta to baking dish, then top with remaining cheese.
• Bake pasta for 15 to 20 minutes or until cheese is lightly browned and pasta is hot.
• Serve pasta immediately, topped with additional fresh basil, if desired. Enjoy!